Negative working electrostatic toners



United States Patent 3,542,681 NEGATIVE WORKING ELECTROSTATIC TQNERSThomas D. Mutafiis, North Plainfield, N.J., asslgnor to GAF Corporation,New York, N.Y., a corporation of Delaware No Drawing. Filed July 10,1968, Ser. No. 743,592 Int. Cl. G03g 9/04 US. Cl. 252-621 9 ClaimsABSTRACT OF THE DISCLOSURE A negative-working electrostatic tonercomposition capable of providing a reverse black and white image 1n anelectrostatic reproduction process comprising an electrically insulatingcarrier liquid, a pigment or coloring agent, e.g. carbon black, and apolymeric material capable of imparting the negative-workingcharacteristics to the electrostatic toner composition. Such a polymericmaterial preferably comprises an alkylated polymer of a heterocyclicN-vinyl monomer.

The present invention relates to a liquid toner com position for use inelectrostatic printing processes; more particularly, the presentinvention relates to a negativeworking liquid toner system comprising inaddition to an electrically conductive carrier liquid, a pigment orcoloring agent, and a polymer which contributes the negative-workingcharacteristics to the toner composition.

In an electrostatic reproduction process a liquid toner is generallyemployed. In such electrostatic processes in which a liquid toner isemployed, a first latent electrostatic image is produced generally on aphotoconductive surface, e.g. zinc oxide, by a first application of anoverall negative charge. This is followed by a discharging through lightexposure so as to leave a negative charge in the unexposed areas. It isat this point that the liquid toner composition is applied. In case ofpositive-working toners, the particles of the toner compositioncomprising the pigment or coloring agent are positively charged, andaccordingly, are directed to the negatively charged areas of the latentimage. In the case of the electrostatic reproduction process brieflydescribed above, this results in the production generally of a black onwhite reproduction through the utilization of positively chargedpigments, e.g. carbon black.

In the case of negative-working toners, however, the particles of toner,e.g. carbon black or similar pigment or coloring agent, are negativelycharged and as such, are repelled by the latent electrostatic image andattracted by the background areas. Using a pigment such as carbon black,therefore, this results in a reverse image from the original andprovides for the production for a white on black print.

In most instances, when a pigment such as carbon black is suspended inan insulating liquid, it assumes mixed low, polarities. As proposed invarious patents the positive polarity of the toner particles can beeasily intensitied by the addition of various control agents to adispersion or suspension of the pigments or coloring agents within theinsulated carrier of the toner composition.

A different problem, however, results when it is desirable forparticular purposes to provide a negativeworking liquid electrostatictoner composition which is capable of providing a reverse image, or moreparticularly, a white on black image in an electrostatic reproductionprocess. Under such circumstances, it is necessary to provide a liquidtoner composition which because of the components thereof, is capable ofbeing attracted to the background area of the latent electrostatic imagewhile being repelled by the latent electrostatic image itself.Accordingly, in order to prepare such a negative- Patented Nov. 24, 1970working electrostatic liquid toner system, it is necessary toincorporate within the basic toner comprising the electricallyconductive fluid and pigment or coloring agent toner particles amaterial which when incorporated in such system, acts to induce strongnegative polarity on the pigment particles so as to be applicablyemployed in the production of the negative or reverse image.

As is well appreciated, the development of suitable materials which canconvert positive-Working toner particles into negative-working particlesis much more difficult than merely accentuating the positivecharacteristics of the toner. Therefore, because of the difiiculty indeveloping a negative-working toner system giving a full, clear negativereproduction print, such toner systems, although extremely desirable forparticular purposes, have not been used to great extent. In thisrespect, as pointed out above, one serious problem of the production ofnegative-working toners is the development of a composition or systemwhich will yield a clear and full reproduction print, that is, onehaving no tendency to streak and containing no bleached out areas.

The above deficiencies and disadvantages of prior art negative-workingliquid toner compositions for electrostatic printing processes have beenovercome in accordance with the present invention through thedevelopment of a negative-working liquid toner system which comprises anelectrically insulating carrier liquid containing a pigment or coloringagent and a polymeric material capable of providing the negative-workingcharacteristics for the liquid toner composition.

Accordingly, it is a principal object of the present invention toprovide such a negative-working liquid toner system for use inelectrostatic printing processes which negative-working liquid tonereliminates the inherent deficiencies and disadvantages of the prior art.

A further object of the present invention is to cornprise such anegative-working liquid toner system comprising an electricallyinsulating carrier liquid, a pigment or a coloring agent, and apolymeric material capable of imparting the negative-workingcharacteristics to the liquid toner composition.

A still further object of the present invention comprises such anegative-working liquid toner composition for use in electrostaticprinting processes comprising an electrically insulating carrier liquid,a pigment, erg. carbon black, and a polymeric material capable ofimparting the negative-working characteristics to the liquid tonercomposition, said polymeric material preferably comprising an alkylatedpolymer of a heterocyclic N-vinyl monomer.

Still further objects and advantages of the novel negative-workingliquid toner composition of the present invention will become moreapparent from the following more detailed description thereof.

The above objects and advantages of the present invention are providedby a liquid negative-working electrostatic toner comprising anelectrically insulating carrier liquid containing a pigment or coloringagent, e.g. carbon black, and a polymeric material capable of impartingthe negative-working characteristics to the toner composition, suchpolymeric material preferably comprising an alkylated polymer of aheterocyclic N-vinyl monomer.

Thus, in accordance with the present invention, the liquid tonercomposition or system comprises as a base fluid any of the conventionalelectrically insulating carrier liquids generally employed in liquiddeveloper and toner compositions. Such electrically insulating carrierliquids generally comprise hydrocarbon solvent materials having thenecessary di-electric constant, e.g. less than 3 and volume resistivity,e.g. in excess of 10 ohm centimeter so as to be acceptably employed inthe electrostatic reproduction process. Thus, for example, the solventcan comprise various hydrocarbon solvents, e.g. toluene, kerosene andmixtures thereof as well as various commercial petroleum and hydrocarbonsolvents, e.g. Isopar having a boiling range of from 300-36 C., orSolveso 100 having a boiling range of from 160174 C., Shell X4 having aboiling range of from 5870 C., or Shell X55 having a boiling range offrom 58140 C., can be effectively employed as the electricallyinsulating carrier liquid of the liquid toner system.

The pigment or coloring agent employed in accordance with thenegative-working liquid electrostatic toner composition of the presentinvention can comprise any of those conventionally employed in positiveor negative-working electrostatic toners. In this respect, thenegative-working characteristics of the toner are associated with theparticular polymeric materials that are included within the liquidsystem and thus, any conventional pigment or coloring agent can beadvantageously employed. Thus for example, the coloring agent or pigmentcan comprise carbon black and various analogous forms thereof, e.g.channel black, furnace black, lamp black and other black materials madeby processes well known in the art, colored pigments including thephosphotungstates and phosphomolybdate colors, alkali blue, and many azopigments as well as m'grosine dyestuffs and triphenyl methane dyes inparticular. Again, these materials are those which are conventionallyemployed in positive-working and negative-Working electrostatic tonercompositions. For purposes of the present invention, however, it ispreferable to employ one of the afore-mentioned carbon black materialswhich provide an excellent black background in the elec trostatic printproduced by employing the liquid toner composition of the presentinvention.

The pigment or coloring agent, e.g. carbon black when suspended in thecarrier liquid as the toner is employed in that amount necessary whenattracted to the background of the negative electrostatic image throughthe negativeworking characteristics of the polymeric material which alsoacts as a dispersing agent because of the surface active characteristicsthereof to be deposited on the background areas and provide desirednegative print or copy. Generally, the pigment comprises from about0.01% to about of the toner system or composition. Of course, slightlylesser or greater amounts can be employed when desired for particularpurposes.

As indicated above, the negative-working characteristics of the liquidtoner composition of the present in- N611ti011 are achieved through theuse of certain polymeric materials which are capable of providing thenecessary negative-working characteristics. As noted previously, suchpolymeric materials preferably comprise alkylated polymers ofheterocyclic N-vinyl monomer.

These materials are those prepared by alkylation of a homopolymer orcopolymer of a heterocyclic N-vinyl monomer, preferably a N-vinyl lactammonomer and most preferably a N-vinyl pyrrolidone monomer with analpha-olefin containing from 2 carbon atoms to 2000 carbon atoms,preferably in the range of from 2 to 200 carbon atoms, and mostpreferably in the range of from 8 to 42 carbon atoms, said alkylationprocess being more fully described in General Aniline & FilmCorporations co-pending patent application, Ser. No. 508,547, filed Nov.18, 1965 and now U.S. Pat. No. 3,417,054, or by simultaneouslypolymerizing and alkylating a mixture containing a heterocyclic N-vinylmonomer, a monoethylenically unsaturated polymerizable monomer and analphaolefin containing from 2 carbon atoms to 2000 carbon atoms or amixture of the same or two different heterocyclic N-vinyl monomers andan alpha-olefin containing from 2 carbon atoms to 2000 carbon atoms,said simultaneous polymerization and alkylation process being more fullydescribed in General Aniline & Film Corporations co-pending patentapplication, Ser. No. 525,374, filed Feb. 7, 1966 and now U.S. Pat. No.3,423,367.

As examples of heterocyclic N-vinyl monomers which contain a carbonylfunction adjacent to the nitrogen in the heterocyclic moiety, whosealkylated polymer derivatives produced as described in saidapplications, Ser. Nos. 508,547 and 525,374, may be employed inpracticing the present invention, that may be mentioned are N-vinylsuccinimide, N-vinyl diglycolylimide, N-vinyl glutarimide,N-vinyl-3-morpholinone, N-vinyl-5-methyl-3- morpholinone,N-vinyl-5-methyl-3-morpholinone, N-vinyl-S-ethyl- 3-morpholinone,N-vinyl oxazolidone, etc., and N-vinyl ringoxygenated lactams asdisclosed in U.S. Pat. 3,231,- 548, and especially the N-vinyl 5-, 6-and 7-membered lactams, particularly N-vinyl pyrrolidone, characterizedby the following formula:

I CH=CH2 rn wherein R and R are selected from the group consisting ofhydrogen, methyl and ethyl, n is an integer of from 1 to 3, and mrepresents the average molecular weight as determined by relativeviscosity measurements which are designated as K values.

The viscosity coefiicient, K, which is fully described in ModernPlastics, vol. 23, No. 3, pp. 157-61, 212, 214, 216 and 218 (1945) iscalculated as follows:

where c is the concentration in grams per 100 ml. of polymer in solutionand the 7 is the viscosity of the solution compared to solvent.

There may also be used the alkylated polymers of comparable monomers ofN-vinyl 5-, 6- and 7-membered thiolactams, N-acryloylpyrrolidone,-piperidone and -caprolactam; N-acryloyl-S-methyl-pyrrolidone,N-acryloyl-6- methyl piperidine and N-acryloyl-7-methyl caprolactam andtheir corresponding 5-, 6- and 7-ethyl derivatives; N-acyloxy-methyl-pyrrolidone, -piperidone and -caprolac tam;N-rnethacryloxy-ethyl-pyrrolidone, -piperidone and -caprolactam;N-methacryloxy-methyl-5-methyl pyrrolidone, -6-methyl-piperidone and-7-methyl-caprolactam; N methacrylamido-methyl-, N-methacrylamidoethyl-,N- methacrylamidopropyland N-(N-phenylacrylamidopropyl)-pyrrolidones,-piperidones and caprolactazms.

The homopolymers of the N-vinyl lactams characterized by the foregoingformula (whose alkylated derivatives obtained, for example, as describedin said application Ser. No. 508,547, are suitable for use in practicingthe present invention) are readily obtained by homopolymerizing N-vinylpyrrolidone; N-vinyl-S-methyl pyrrolidone; N-vinyl-S-ethyl pyrrolidone;N-vinyl-'5,5-dimethyl pyrrolidone; N-vinyl-5,5-diethyl pyrrolidone andN- vinyl-5-methyl-5-ethyl pyrrolidone; N-vinyl piperidone; N-vinyl-methyl piperidone; N-vinyl-6-ethyl piperidone; N-vinyl-6,6-dimethyl piperidone; N-vinyl-6,6-diethyl piperidone andN-vinyl-6-methyl-6-ethyl piperidone; N-vinyl caprolactam,N-vinyl-7-methyl caprolactam; N-vinyl-7,7- dimethyl caprolactam;N-vinyl-7-ethyl caprolactom; N- vinyl-7,7-diethyl caprolactam andN-vinyl-7-methyl-7-ethyl caprolactam.

For the purpose of the present invention I employ alkylated derivativesof homopolymers of heterocyclic N- vinyl monomers having a K value fromabout 10 to 140, preferably from about 30 to 100. These homopolymers arereadily obtained by conventional homopolymerization procedures of theforegoing heterocyclic N-vinyl monomers described in U.S. Pats.2,265,450; 2,317,804; 2,335,454 and many other too numerous to mentionin which working examples are given.

Copolymers obtained by copolymerizing 5 to 99 mole percent of theforegoing heterocyclic N-vinyl monomers with 1 to mole percent of amonoethylenically unsaturated polymerizable monomer and having a K valuefrom about to 140 are readily alkylated in accordance with the presentinvention to yield products having solubility characteristics dictatedby the end use.

The various monoethylenically unsaturated polymerizable monomers, whichare copolymerized with any one of the aforementioned heterocyclicN-vinyl monomers in the conventional manner and which will yieldcopolymers that are readily alkylated in accordance with saidapplication, 'Ser.,No. 508,547, to produce alkylated copolymersalkylated copolymers suitable for use'in practicing the presentinvention, include vinyl esters such as vinyl acetate, vinyl propionate,vinyl butyrate, vinyl isobutyrate, vinyl lactate, vinyl caproate, vinylcaprylate, vinyl oleate and vinyl stearate; acrylonitrile; vinylketones; vinyl cyclohexane; styrene; 2-vinyl pyridine, 4-vinyl pyridine;acrylic acid, acrylate ester monomers of the formula:

OHFCHCOO-R wherein R represents either a straight or branched alkyl offrom 1 to 18 carbon atoms or an alkoxyalkyl in which the total number ofcarbon atoms in the alkyl groups range from 3 to 6.

As examples of such acrylate esters the following are illustrative:methyl, ethyl, propyl, isopropyl, butyl, isobutyl, s-butyl,2-methyl-1-butyl, 3-methyl-1-butyl, Z-ethyll-butyl, amyl, 3-pentyl,2-methyl-1-pentyl, 4-methyl-2- pentyl, hexyl, 2-ethyl-hexyl, heptyl,2-heptyl, octyl, 2- octyl, nonyl, 5-ethyl-2-nonyl, decyl,2-methyl-7-ethyl-4- undecyl, dodecyl, tetradecyl, hexadecyl, octadecyl,2- methoxyethyl, 2-ethoxyethyl and 2-butoxyethyl acrylate; methacrylicmonomers such as methacrylic acid, methyl methacrylate, cyclohexylmethacrylate, isobutyl methacrylate, isoamyl methacrylate, B-methoxyethyl methacrylate and a-(o-chlorophenyl) ethyl methacrylate, B-phenoxyethyl methacrylate, u-phenyl ethyl methacrylate, phenyl methacrylate,o-cresol methacrylate, p-cyclohexylphenyl methacrylate, 2-nitro-2-methylpropyl methacrylate, diethylaminoethylmethacrylate, ethylidene acetatemethacrylate and glycidyl methacrylate, including esters of halo acrylicacids, such as methyl-Z-chloro-acrylate, ethyl-achloro-acrylate,phenyl-a-chloro-acrylate, a-ethylacrylic acid; methacrylonitrile;N-alkyl and N-aryl substituted acrylamides such as N-methyl acrylamide,N-ethyl acrylamide, N-propyl acrylamide, N-n-butyl acrylamide,N-ndodecyl acrylamide, N-n-octadecyl acrylamide, N-N-dimethylacrylamide, N,Ndiethyl acrylamide, N-N-di-nbutyl acrylamide,N-N-di-isobutyl acrylamide, N-cyclohexyl acrylamide, N-N-dicyclohexylacrylamide, N-phenyl acrylamide, N-p-nitro-phenyl acrylamide,N-a-naphthyl acrylamide, N-fi-naphthyl acrylamide, N-methyl-N-phenylacrylamide, N,N-diphenyl acrylamide, N-benzyl acrylamide, N,N-di-benzylacrylamide; and grafted monomers of the type disclosed in US. Pats.3,029,219; 3,035,009; 2,036,033 and the like.

A mixture consisting of from 5 to 99 mole percent of any one of theforegoing heterocyclic N-vinyl monomers and from 1 to 95 mole percent ofa different heterocyclic N-vinyl monomer, such as for example, N-vinyllactam with either N-vinyl succinimide, N-vinyl-3-morpholinone, and thelike, may also be copolymerized and the resulting copolymer alkylatedfor use in the present invention.

From numerous experiments connected with the present invention, it hasbeen found that the configuration of the foregoing monoethylenicallyunsaturated monomers, and numerous others, is immaterial since they allcopolymerize in the afore-mentioned proportions with the heterocyclicN-vinyl monomers and yield copolymers which are soluble in the organicsolvent or mixture thereof and which are readily alkaylated.

With regard to the a-olefins employed for producing the alkylatedpolymers used in practicing this invention, it is to be noted at theoutset that any a-olefins having a molecular weight from about 28 to ashigh as about 28,000, may be employed as the alkylating agent for thealkylated polymers of the various heterocyclic N-vinyl monomers. Asexamples of such a-olefins, the following are illustrative; ethylene,propylene, l-butene, l-pentene, 2-ethyl-l-butene, 2-methyl-l-pentene,l-hexene, S-methyl-l-hexene, Z-methyl-l-pentene, 3-ethyl-1-pentene,l-heptene, l-octene, l-nonene, 2-ethyl-1-hexene, l-decone, 1- dodecene,l-tetradecene, l-hexadecene, l-heptadecene, loctadecene, 1-nonadecene,l-eicosene, l-docosene, l-tetracosene, l-pentacosene and polybutenes ofmolecular weight of 400 to 2500 may be employed.

While linear a-olefins are preferred because of their commercialavailability, numerous isomers of a-olefins ranging from l-pentene tol-pentacosene as well as polybutenes may also be employed in thealkylation reaction. The only requirement in such case is that theisomer contained in ethylenic unsaturation in the a-position thereof.

Instead of employing any one of the foregoing individual u-olefins, amixture of commercially available linear a-olefins produced by crackingpetroleum wax or by polymerizing lower olefins may also be used as thealkylating agent. Alpha-olefins in the carbon range of from C6-C7;CIT-C9; Cg-C11; C11C15' and C5-C2) are commercially available and may beused. A mixture of u-olefins containing from 65 to 75 percent ofa-olefins of from C to C carbon atoms having an average molecular Weightof 366 is also commercially available and such mixture is employed inthe alkylation reaction.

In addition to the preferred employment as the polymeric material of thealkylated polymers of N-vinyl monomers, and in particular, vinylpyrrolidone monomers, any and all materials capable of imparting thenecessary negative-working characteristics to the liquid toner systemcan be advantageously employed. Thus for example, the materials inaccordance with the present invention can comprise natural hydrocarbonpolymers, e.g. Gilsonite resins, thermoplastic polymers of unsaturatedhydrocarbons derived from petroleum cracking, e.g. Piccopale resins andoil-soluble C-alkyl succinyl derivatives of polyethyleneimine, e.g.penta or tetra-ethylene imine wherein the alkyl group contains 50 ormore carbon atoms, e.g. Oronite resins for example, Oronite 1200 asdisclosed in US. Pats. 3,219,666 and 3,163,603. All of such materialspossess surface active characteristics and thus provide the necessarydispersion of the toner particles in the liquid toner system. Moreimportantly, however, all of such materials possess the property ofconverting the toner system or composition into a negative-workingcomposition effectively employable in electrostatic printing processesfor producing reverse or negative reproductions.

Accordingly, the polymeric materials employed in accordance with thepresent invention to provide the necessary negative-workingcharacteristics to the liquid toner composition are generally thoseselected from the group consisting of alkylated polymers of N-vinylmonomers, e.g. alkylated polymers of N-vinylpyrrolidone polymers,natural hydrocarbon polymers, e.g. natural bitumen, thermoplasticpolymers of unsaturated hydrocarbons from petroleum cracking, andoil-soluble C-alkyl succinyl derivatives of polyethylene imines.

The amount of such material capable of imparting the negative-workingcharacteristics to the liquid toner composition employed for a givenamount of pigment or color ing agent is not critical in accordance withthe present invention, such material being employed only in that amountnecessary to provide the necessary negative-Working characteristicswhile maintaining a stable suspension or dispersion of the toner.Generally, such material is employed in the range of 0.01-2-3 times theweight of the pigment or coloring agent, and preferably within the rangeof 1 to parts per 100 parts of the pigment employed.

In accordance with the present invention, the manner by which the liquidtoner composition is produced is in no way critical and, accordingly,such composition can be prepared by conventional methods well known inthe art.

In this respect, it has been found that a 3-roll mill, ball mill,colloid mills, high speed shear mixers, etc., are all applicable in theproduction of the dispersions employed in the liquid electrostatic tonersystem of the present invention. Thus for example, it is conventional toproduce a concentrate or ink of the toner and material capable ofimparting negative-working characteristics to the composition in aninsulating carrier liquid, and subsequently adding such concentration orink to further insulated carrier liquid to provide the liquid tonercomposition employed in the electrostatic reproduction process.

The present invention wil now be described by reference to the followingspecific examples. It is to be understood, however, that such examplesare presented for purposes of illustration only, and the presentinvention is in no way to be deemed as limited thereto.

EXAMPLE I The following materials were mixed on a 3-roll mill to obtaina uniform dispersion as a heavy ink, by passing over the 3-roll mill 8times:

1 An olefin-alkylated polyvinylpyrrolidone of an average olefin carbonchain length of 16 carbon atoms and 20% vinylpyrrolidone residue.

An aliphatic petroleum solvent having a boiling range of 300-360 F.

The ink was adjusted to carbon black content with the addition of afurther amount of the electrically insulating carrier liquid and, thefinal toner system was provided by adding 7 cc. of the 5% toner to 1liter of addi tional aliphatic petroleum solvent.

The toner composition was then employed in a conventional electrostaticcopier to produce a negative electrostatic reproduction. The printproduced by the use of the toner composition of the present inventionwas found to give a clear reproduction of the original having a reverseimage, that is, the background areas of the reproduction were blackwhereas the printed material on the original was white. A copy havinggood fill and substantially no tendency to streak was obtained.

EXAMPLE II Example I is repeated except that the material employed toimpart the negative-Working characteristics to the liquid tonercomposition is replaced by a substantially equivalent amount of thefollowing materials:

Ganex 220 1 Oronite 1200 2 Piccopale resin 3 Gilsonite 4 Anolefin-alkylated polyvinylpyrrolidone of an average olefin carbon chainlength of 20 carbon atoms and 20% vinylpyrrolidone residue.

2 An oil-soluble C-alkyl succinyl derivative of pentaethylene innnehaving 50 or more carbon atoms in the alkyl chain.

{A thermoplastic polymer of an unsaturated hydrocarbon der1ved frompetroleum.

A natural hydrocarbon polymer-natural bitumen.

In all cases, when such materials are employed in lieu of the alkylatedpolymer of the N-vinyl monomer, substantial equivalent results areobtained and a negative-working electrostatic toner providing full,clear negative prints is obtained.

While the present invention has been described primarily with respect tothe foregoing specific examples, it is to be understood that the presentinvention is in no way to be deemed as limited thereto, but must beconstrued as broadly as all or any equivalents thereof.

What is claimed is:

1. A negative-working electrostatic liquid toner consisting essentiallyof (a) an electrically insulating carrier liquid having a dielectricconstant of less than 3 and a volume resistivity in excess of 10 ohmcentimeter; (b) a coloring agent dispersible in said carrier liquid andcapable of yielding color copies when repelled \by a negative latentimage; and

(c) as a polymer capable of imparting negative-working characteristicsto said toner, an alkylated polymer of a heterocyclic N-vinyl monomer inwhich the alkyl radical of said polymer contains from 2 to 2000 carbonatoms and said polymer has a K value of about 10 to 140.

2. A toner as defined in claim 1 wherein said coloring agent is apigment.

3. A toner as defined in claim 2 wherein said pigment is carbon black.

4. A toner as defined in claim 1 wherein said carrier liquid is ahydrocarbon.

5. A toner as defined in claim 1 wherein said alkyl radical of saidpolymer contains 8 to 42 carbon atoms.

6. A toner as defined in claim 1 wherein said alkylated polymer is analkylated polymer of an N-vinylpyrrolidone monomer.

7. A toner as defined in claim 6 wherein said coloring agent is apigment.

8. A toner as defied in claim 7 wherein said pigment is carbon black.

9. A toner as defined in claim 4 wherein said carrier liquid is ahydrocarbon.

References Cited UNITED STATES PATENTS 3,079,270 2/ 1963 Cortez 252-62.1

FOREIGN PATENTS 938,293 1963 Great Britain. 993,150 1965 Great Britain.944,345 1963 Great Britain. 944,394 1963 Great Britain.

GEORGE E. LESMES, Primary Examiner J. P. BRAMMER, Assistant Examiner

